Although inflammation is an essential host defense mechanism during lung infection, its timely resolution is critical for the host to prevent lung injuries resulting from uncontrolled inflammatory cells. Recently we discovered that MUC1, one of the membrane-tethered mucins expressed on the apical surface of airway epithelial cells, has an ability to control inflammation at the end of airway Pseudomonas aeruginosa (Pa) infection by suppressing toll-like receptor (TLR)5 signaling. In this renewal application, we propose to elucidate the mechanism by which MUC1 suppresses TLR5 during Pa infection. We hypothesize that MUC1 suppresses TLR5 signaling during Pa infection by a direct interaction with TLR5 which is mediated through activation of EGFR and propose the following aims to test the hypothesis. In Aim 1, we will determine whether anti-inflammatory effect of MUC1 during airway Pa infection is due to its direct interaction with TLR5 by examining the details of molecular interactions between MUC1 and TLR5 in cultured epithelial cells using both genetic and immunological methods. In Aim 2, we will determine whether the interaction of MUC1 with TLR5 is regulated by tyrosine phosphorylation of MUC1 by EGFR in cultured cells using genetic as well as immunological methods and such role of EGFR will be verified using EGFR deficient mice. In the final Aim 3, the complete sequence of the events that take place from Pa infection to the resolution of inflammation by MUC1 will be monitored in real time using both cultured cells and in vivo animals. Successful completion of these experiments will provide the detailed molecular interactions associated with the anti-inflammatory role of MUC1 during airway Pa infection and should provide insights into possible therapeutic strategies to control excessive and prolonged lung inflammation characteristic of chronic inflammatory lung diseases such as COPD and cystic fibrosis. PUBLIC HEALTH RELEVANCE: Chronic lung inflammatory diseases such as COPD, asthma and cystic fibrosis develop as a result of failure to control lung inflammation in a timely manner. MUC1 is a new anti- inflammatory molecule that prevents excessive inflammation during airway infection. Understanding how MUC1 controls excessive lung inflammation will help us to better understand the pathophysiology of these lung diseases and may provide insights into possible therapeutic strategies to treat these inflammatory lung diseases.